Sarcastic is where you say what you don't mean.
example:
"I love that dress you're wearing." (this would be said in a way that makes it sound sarcastic and so you don't love the dress, you actually hate it)

Example sentences using "Sarcastic"

I was just being sarcastic.
I love using sarcasm.
He's so often sarcastic that I never know when he's actually serious.
Sarcasm offends some people.
Stop being sarcastic.
Even though you were being sarcastic, I still think what you said was rude.

She gave him a sarcastic smile.
His tone hung somewhere between sarcastic and annoyed.
Was he being sarcastic, or was he still miffed about the losing the mules?
"Wonderful," was the sarcastic response.
He said in a sarcastic tone.

The only example for ‘I was sarcastic’ would be if you were talking about the type of person you are, as if you were a sarcastic person. Other then that ‘I was being sarcastic’ would refer to what you said previously was said sarcastically.

こんばんは！🙂
I think there is just one word to change. "on" should be "about".
If I want to make a sarcastic remark about someone or something really disgusting, I should use polite language, and never ever make grammatical mistakes. If I failed, it would make me feel utterly awkward and boneheaded.
"really" goes better with disgusting, and "that is" is optional.
"never ever" is fine.
"disgusting" is quite a specific word, "objectionable" might be better but it depends on what you have in mind. 🙂